例句：
It has a clean and usable interface and has an Extensions API to extend and customize your installation.
它有一个清爽和可用的接口，并且还有一个扩展的API可以定制你的安装。
Someone came out with a most useful suggestion.
有人提出了一个非常有益的建议。
Please cancel the words which are useless.
请把无用的词划掉。